This section delves into the interplay between diet and physical activity, emphasizing the significance of micronutrients (vitamins and minerals) in promoting health and peak physical performance. The discussion is rooted in evidence pointing to increased activity of micronutrient-dependent metabolic pathways, biochemical adaptations in tissues, and elevated turnover rates during physical activity.

Micronutrients, despite their small food content compared to macronutrients, play crucial roles as components of proteins, enabling complex reactions necessary for utilizing potential energy in macronutrients. The Dietary Reference Intakes (DRIs) are introduced as recommendations to prevent nutritional inadequacy and deficiency, with the Recommended Dietary Allowance (RDA) meeting the needs of 98% of healthy individuals.

The section aims to provide an overview of the biological roles of vitamins and minerals in supporting physiological functions during exercise. It underscores the effects of reduced micronutrient status on physical performance measures and identifies key points at which micronutrients influence metabolism during physical activity. Additionally, the chapter outlines the consequences of diminished micronutrient intake on physical activity.

The discussion then shifts to micronutrient requirements for athletes, encompassing both vitamins and minerals. These micronutrients contribute to the formation of bioactive compounds, facilitating energy production and utilization, oxygen transport, fluid balance regulation, and protection against oxidative damage. The B vitamins and certain minerals are highlighted for their roles in carbohydrate metabolism for muscle work, red blood cell formation, oxygen transport, and other essential functions during physical activity.

The evaluation of micronutrient needs for optimal physical performance is emphasized, requiring a concurrent assessment of nutrient intake and biochemical measures of nutritional status. The limitations of relying solely on self-reported food intake are acknowledged, emphasizing the importance of utilizing appropriate DRIs to assess micronutrient adequacy. The section concludes by presenting an overview of how subclinical deficiencies in minerals like zinc, iron, riboflavin, and magnesium can lead to reductions in exercise performance and markers of performance. Overt clinical deficiency is deemed rare without excess loss or impaired absorption.

Vitamins and Performance

Thirteen essential vitamins, classified as water or fat-soluble, play a crucial role in sustaining life. This section emphasizes the significance of adequate B vitamin intake, particularly the water-soluble ones, in optimizing energy production and facilitating the building and repair of muscle tissue. The B-complex vitamins are noted for their diverse functions related to exercise, including energy production, red blood cell generation, protein synthesis, and tissue maintenance, including the central nervous system. While the pivotal roles of vitamins in these processes are acknowledged, the narrative points out the limited direct evidence linking vitamin intake to ergogenic benefits for athletes. Nevertheless, certain vitamins, such as E and C, are suggested to aid athletes in tolerating training better and maintaining a healthy immune system during intensive training.

Water-Soluble Vitamins: This subsection delves into the characteristics of water-soluble vitamins, comprising eight B vitamins and vitamin C. Their solubility in water is highlighted, limiting their storage in the body for extended periods and leading to excess excretion in urine when taken in supplement form.

Thiamin (Vitamin B1): Thiamin’s role as a coenzyme in carbohydrate and protein metabolism for energy production is detailed. Thiamin pyrophosphate, its biologically active form, is highlighted for its participation in the Krebs cycle during oxidative energy production, especially in exercise. Thiamin sources in various foods are outlined, emphasizing its wide distribution. The Recommended Dietary Allowance (RDA) for thiamin is provided, with related energy intake considerations. The potential risk of low thiamin status in female gymnasts and wrestlers, particularly those on low-energy diets, is discussed. Contrasting findings from studies on thiamin intake and its impact on muscle strength and running performance are presented, indicating a lack of consistent evidence for the ergogenic benefits of supplemental thiamin.

The section concludes by underscoring the need for further research to establish clearer links between vitamin intake, especially B vitamins, and enhanced athletic performance. Despite recognizing the vital functions of these vitamins, the narrative maintains a cautious stance on extrapolating their direct ergogenic benefits for athletes based on the current body of evidence.

Riboflavin

Riboflavin, commonly known as vitamin B2, operates within the mitochondrial electron transport system as the coenzymes flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD). These coenzymes play a crucial role in electron transfer, converting breakdown products of carbohydrates and fats into adenosine triphosphate (ATP). Additionally, riboflavin is essential for the conversion of vitamin B6 to its active form. Various food sources rich in riboflavin are highlighted, ranging from dairy products and lean meats to vegetables and nuts. The Recommended Dietary Allowance (RDA) for riboflavin intake, differentiated by gender and energy intake, is presented.

Athletes and Riboflavin: The section notes that athletes generally maintain adequate riboflavin levels, except for specific cases such as female gymnasts. It explores the impact of physical training on riboflavin needs, indicating a decrease in riboflavin status during training. Metabolic studies, particularly those comparing different riboflavin daily intakes, reveal reduced riboflavin status with lower intake levels. Despite this, studies indicate that adequate riboflavin intake does not necessarily result in performance differences, emphasizing the need for nuanced interpretation.

Niacin (Vitamin B3): Niacin, or vitamin B3, is detailed as existing in two forms, nicotinic acid and nicotinamide, both metabolized to form essential coenzymes. These coenzymes play crucial roles in various metabolic pathways, including the breakdown of carbohydrates, fats, proteins, and glycogen to produce ATP. The section emphasizes niacin-rich food sources such as meats, fish, and whole-grain products. RDAs for niacin are provided for men and women, with a cautionary note against supplementation exceeding recommended doses due to potential adverse effects on fat mobilization and aerobic endurance performance.

Vitamin B6 (Pyridoxine): Vitamin B6, encompassing various biologically active forms, is explored for its role as a cofactor in amino acid transformation and glycogen regulation during exercise. High-protein foods are identified as rich sources of B6, and RDAs are provided based on gender. The section discusses the prevalence of decreased B6 status in athletes, influenced by factors like low energy intake and poor food choices. Despite varied B6 status among athletes, studies show that aerobic endurance performance may not change significantly with different B6 intake levels.

Folate (Vitamin B9): Folate, or vitamin B9, is highlighted for its role as a coenzyme in critical processes such as DNA synthesis, amino acid metabolism, cell repair, and red blood cell formation. Dietary sources of folate are outlined, and the RDA is provided. Discrepancies in folate status among active men and women, particularly female aerobic endurance athletes, are discussed. Folate supplementation effects on physical performance are explored, revealing mixed results in hematological parameters without significant improvements in treadmill performance, cardiorespiratory function, or metabolic response during exercise.

Vitamin B12 (Cobalamin): Vitamin B12, or cobalamin, serves as a coenzyme in the transfer of methyl groups for DNA formation, particularly in collaboration with folate for hemoglobin formation. The section notes the exclusive presence of B12 in animal-based foods and provides the adult RDA. While intakes of B12 were found to be low in female aerobic endurance athletes, evidence supporting improved performance through B12 supplementation is lacking. Early studies demonstrated no enhancement in running performance or work capacity with B12 supplementation, emphasizing the need for cautious interpretation of supplementation outcomes.

Other B Vitamins and Vitamin C

Pantothenic Acid and Biotin: Pantothenic acid, a component of coenzyme A crucial for energy production in the Krebs cycle, and biotin, a coenzyme involved in amino acid metabolism and gluconeogenesis, are discussed. Food sources for each, including meats, eggs, legumes, and whole grains for pantothenic acid, and egg yolks, liver, vegetables, nuts, and soybeans for biotin, are highlighted. The Recommended Dietary Allowances (RDAs) for pantothenic acid (5 mg) and biotin (30 μg) are provided. Limited data on usual intakes and biochemical indicators are noted. Supplementation studies on pantothenic acid reveal no significant effects on metabolic responses or performance, while data on biotin supplementation effects are unavailable.

Choline: Choline’s role as a neurotransmitter and methyl donor in creatine formation and lipid transport is explained. The influence of exercise on plasma choline levels and the potential performance improvement with regular choline supplementation during prolonged exercise are mentioned. However, the need for further studies to validate and replicate these performance improvements is emphasized.

Vitamin B Complex: The cumulative impact of B vitamins on energy metabolism prompts exploration of their combined effects on physical performance. Research reveals that the simultaneous restriction of thiamin, riboflavin, and B6 in the diet significantly reduces peak aerobic capacity, peak power, and hastens blood lactate accumulation in trained male cyclists. This underscores the importance of viewing B vitamins collectively for optimal performance.

Vitamin C (Ascorbic Acid): Vitamin C, also known as ascorbic acid, is detailed for its various biological functions that can impact physical performance. While not directly influencing enzyme actions, vitamin C is essential for synthesizing catecholamines and carnitine, reducing inorganic iron for absorption, and acting as a potent antioxidant. Food sources, including fruits and vegetables, are listed. The RDAs for men (90 mg) and women (75 mg), along with increased vitamin C needs during physiological stressors, are provided. Despite adequate intake by many athletes, a significant percentage, particularly male collegiate athletes and female aerobic endurance athletes, consume less than the RDA. Studies demonstrate the impact of low vitamin C status on performance, emphasizing its significance for work capacity, efficiency, and aerobic power during exercise.

Fat-Soluble Vitamins: A, D, E, and K

Vitamins A, D, E, and K, associated with dietary fat sources and stored in adipose tissue, play distinct roles despite having no direct involvement in energy production. While vitamins A and E act as antioxidants, aiding in reversing age-related protein synthesis declines, vitamin D’s connection to muscle strength is explored. Vitamin K, although lacking evidence linked to physical performance, completes the quartet of fat-soluble vitamins.

Vitamin A: Vitamin A, in its active form as retinol, protects epithelial cells, aids vision, and supports immune function. Found in liver, butter, eggs, and fortified dairy products, its precursor beta-carotene is present in yellow-orange and dark green leafy vegetables. The Recommended Dietary Allowances (RDAs) for men (900 RE or 4,500 IU) and women (700 RE or 3,500 IU) are generally met by athletes. However, some studies suggest inadequate vitamin A intake in certain groups, attributed to fat avoidance. The impact of vitamin A supplementation on physical performance remains minimally explored, with early studies showing no significant changes in running performance.

Vitamin E: Vitamin E, encompassing tocopherols and tocotrienols, acts as a crucial antioxidant in cell membranes. Derived from vegetables, nuts, whole grains, and wheat germ, its RDA for adults is 15 mg of α-tocopherol. Athletes often meet RDAs, but when dietary sources alone are considered, some fall short. Supplemental vitamin E’s effects on physical performance are inconsistent across studies, showing no significant enhancement. While athletes generally maintain adequate intake, potential benefits in reducing oxidative stress remain inconclusive when combined with vitamin C.

Vitamin D: Also known as cholecalciferol, vitamin D primarily influences calcium absorption and bone metabolism. Epidemiological data hint at its role in muscle strength, with deficiency linked to musculoskeletal pain and neuromuscular dysfunction. Food sources include fortified dairy, eggs, and various fish. Adequate intake for adults is 5 μg (200 IU). Vitamin D receptors in skeletal muscle raise interest in its connection to physical performance, particularly as athletic performance appears to correlate with vitamin D levels. Athletes practicing indoors, avoiding sun exposure, may be at risk for decreased vitamin D levels. Associations between low vitamin D status and impaired strength in various age groups await further investigation, as does the exploration of supplemental vitamin D’s impact on strength gains.

Minerals and Performance

Minerals, inorganic elements categorized as microminerals and trace elements, play vital roles in various physiological processes. Macrominerals, including sodium, potassium, chloride, calcium, phosphorus, magnesium, and sulfur, with recommended intakes exceeding 100 mg/day, significantly influence bodily functions. This section delves into the impact of iron, magnesium, zinc, and chromium on physical performance, emphasizing findings post-publication of Dietary Reference Intakes (DRIs) for minerals.

Macrominerals: Macrominerals, constituting over 4% of body weight, encompass calcium, phosphorus, magnesium, sodium, chloride, and potassium. Sodium, potassium, and chloride, existing as electrolytes in body fluids, maintain fluid balance, nerve function, and impulse transmission. Individualized sodium intakes may be influenced by factors like sweat rate and exercise-induced losses. Calcium and phosphorus, crucial for bone formation, also play roles in nerve conduction, muscle contraction, and energy utilization. Adequate intake recommendations guide these minerals, but the impact of calcium supplementation on testosterone production in athletes yielded inconclusive results.

Magnesium: Magnesium, primarily found in bones and serving as a component of numerous enzymes, regulates physiological processes like energy metabolism and gluconeogenesis. Dietary sources include fruits, vegetables, nuts, seafood, and whole-grain and dairy products. While dietary surveys reveal varied magnesium intakes among athletes, with some falling below recommendations, magnesium loss increases after intense exercise. Supplementation in competitive athletes has shown positive effects on cellular function, including decreased creatine kinase levels and improved performance indicators. Alterations in dietary magnesium intake can impact performance, as evidenced by changes in heart rate and work efficiency during submaximal exercise in individuals with low magnesium intake.

Minerals, both microminerals and trace elements, contribute significantly to physical performance. While some aspects of macromineral interactions with performance are well-documented, further research is needed, especially regarding the impact of trace elements and specific minerals like copper, phosphorus, selenium, iodine, molybdenum, potassium, and chloride on athletic performance. The exploration of the interplay between mineral intake, status, and physical performance continues to advance our understanding of this critical relationship.

Trace Elements

Introduction: Trace elements, occurring naturally in soil, plants, and animals in minute concentrations, are essential for optimal health and performance. This section explores the significance of iron, copper, and zinc, highlighting their roles in physiological processes and their impact on athletic performance.

Iron: Iron, a critical metallic element, plays a crucial role in oxygen transport and utilization. Hemoglobin, myoglobin, and various enzymes are iron-containing compounds vital for oxygen metabolism. While heme iron from animal sources is better absorbed, nonheme iron from plant-based foods faces absorption challenges influenced by dietary components. Iron deficiency, prevalent in female athletes, can occur in stages, impacting performance and metabolism. Supplementation has shown positive effects, reducing muscle fatigue and improving aerobic endurance performance.

Copper: Copper serves as a metalloenzyme essential for nonheme iron uptake, hemoglobin formation, energy production, and antioxidant activity. Despite its potential influence on performance, clear evidence of impaired performance due to inadequate copper intake is lacking. Widely distributed in various foods, copper’s recommended daily intake for adults is 900 μg/day for both males and females.

Zinc: Zinc, present in numerous enzymes throughout the body, regulates energy metabolism, growth, immune function, and wound healing. Diets high in protein provide substantial zinc amounts, but its availability is reduced in high-fiber and phytic acid-rich diets. Physically active adults generally meet the recommended daily intake, but female athletes in certain sports may have marginal intakes. Low zinc status is linked to decreased muscle strength and endurance, impacting fast-twitch glycolytic muscle fibers. Studies indicate that zinc supplementation can enhance muscle function, strength, and endurance, emphasizing its role in physical performance.

Trace elements, including iron, copper, and zinc, are integral to physiological processes crucial for athletic performance. While iron deficiency stages have noticeable effects on performance, copper’s impact is less clear. Zinc, however, demonstrates a clear connection between low status and decreased muscle function, making it a key element in the optimization of physical performance. Ongoing research continues to uncover the intricate relationship between trace elements and athletic excellence.

Selenium: Selenium, present as selenoproteins, plays a crucial role in protecting cells from oxidative damage, functioning as glutathione peroxidase. Collaborating with vitamin E, it acts as an antioxidant. Despite these important roles, evidence supporting a direct link between selenium and athletic performance is currently lacking. The selenium content in the diet is closely tied to protein intake, with foods like seafood, meats, whole grains, liver, and certain vegetables contributing to selenium levels. The Recommended Dietary Allowance (RDA) for selenium is set at 55 μg/day for adult males and females.

Chromium: Chromium’s potential to enhance insulin action in individuals with insulin resistance has been suggested by emerging evidence. However, its role in promoting physical performance remains a topic of controversy. Food sources rich in chromium include whole grains, cheese, beans, mushrooms, oysters, wine, apples, pork, chicken, and brewer’s yeast. Chromium is considered provisionally essential, with recommended intakes of 35 and 25 μg/day for men and women, respectively. Assessing dietary chromium and its nutritional status is challenging, limiting the evaluation of its significance in physical activity. Numerous studies on supplemental trivalent chromium, commonly as chromium picolinate, have yielded inconsistent results regarding its impact on strength gain, muscle accretion, or glycogen synthesis after exercise in healthy individuals.

Other Minerals: Various minerals like boron, vanadium, cobalt, fluoride, iodine, manganese, and molybdenum theoretically possess biological functions that could influence performance when consumed in suboptimal amounts. However, there is a notable absence of published research providing evidence that restricted intakes of these minerals actually have negative effects on physical performance. While vanadium and manganese play roles in carbohydrate and lipid metabolism in animals, human dietary deficiencies are rare. The professional exploration of these minerals and their impact on athletic performance requires further investigation and comprehensive research.